Known systems of interconnected detectors usually incorporate three wire cables which provide AC energy to each of the detectors via two of the wires. The third wire is used for signaling. When one detector goes into alarm, it can signal via the third wire, its alarm state to all other detectors in the system. The remaining detectors then go into alarm.
When detector systems are installed, during construction, after testing the detectors are usually removed for safekeeping. They must then be reinstalled subsequently for occupancy. Known detectors for such systems incorporate a base and a separable head which carries a sensor and control electronics.
Each base is permanently mounted on a surface, such as a ceiling. In one known system, a three wire cable is connected to three contacts on each base. Each base exhibits three electrical contacts, two for AC and one for signaling.
Each of the heads can slidably engage a base. Three electrical contacts on a respective head, two for AC and one for signaling, slidably engage corresponding contacts on the base as the head is being installed.
The presence of contacts on the base and head tends to create installation and maintenance issues. The contacts must be kept clean, not always easy to do during construction, and installation personnel must be able to clean particulate matter from the base as needed prior installing the heads.
There continues to be a need for electrical signal transfer systems usable with interconnected detectors. Preferably such transfer systems would alleviate at least some of the cleanliness problems of known detector systems. It would also be preferable if such transfer systems did not substantially increase unit costs or create manufacturing complexity.